- Add 'Add to Theseus (jenin)' button in admin orders expanded view
- POST /admin/orders/:id/theseus creates a letter in the 'scraps' queue on mail.hackclub.com
- Uses item name as rubber stamps, order shipping address for recipient
- Saves letter ID (ltr!xxx) as tracking number with clickable link to Theseus back office
- Idempotency key prevents duplicate letters
- Add THESEUS_API_KEY to config and .env.example
DM @jenin on Slack for env vars
